Method for removing oxygen from a gas stream

ABSTRACT

A process for removing oxygen from a gas stream and a method of controlling the process are provided herein. The deoxygenation process of the present invention may include the steps of combining a feed stream, such as a natural gas feed stream, with hydrogen and contacting the combined stream with a catalyst composition under conditions sufficient to remove at least a portion of the oxygen from the combined gas. In some cases, the catalyst composition can comprise copper and the conditions of the contacting may be such that at least a portion of the copper remains in a reduced state during deoxygenation. The method of controlling the deoxygenation process described herein includes utilizing measured values of parameters of the deoxygenated stream to control one or more parameters of the feed gas stream introduced into the deoxygenation zone and achieve a desired level of oxygen removal.

FIELD OF THE INVENTION

This invention relates to systems and methods for removing oxygen from agas stream. In another aspect, embodiments of this invention also relateto methods for controlling such processes.

BACKGROUND

Natural gas is widely used as a fuel source and has many commercial,residential, and industrial applications. Primarily produced fromsubterranean formations, natural gas often includes undesiredconstituents such as sulfur, water, nitrogen, carbon dioxide, and/oroxygen. In some cases, these components are naturally-occurring as aresult of the particular formation from which the gas was produced. Inother cases, these contaminants can enter the gas stream as a result ofthe methods or systems used to facilitate production of the gas from theunderground deposit or as a result of its transportation from onelocation to another.

Oxygen is one component often present in natural gas, especially naturalgas produced from mature fields, that is desirable to remove. Early inthe life of a gas deposit, sufficient pressure typically exists for thenatural gas to flow freely from the formation. As the field matures andthe gas is depleted, the pressure of the deposit decreases and the gasmust be extracted from the formation. At times, oxygen may enter the gasstream as a result of the extraction methods used, typically throughleaks in the removal or transport system. Allowed to remain in highconcentrations in the natural gas stream, oxygen contributes tocorrosion (especially in the presence of residual water) and may alsocause undesired side reactions in downstream processing equipment, whichmay lead to excessive equipment shut downs and lost production. As aresult, producers must remove excess oxygen from natural gas in order tomeet pipeline specifications, which typically limit oxygen contents to50 parts per million by volume (ppmv) or less.

Blending is one method used by producers to incorporate highoxygen-content gas into a pipeline-compliant product, although thevolume of low-oxygen gas required to produce an on-specification productseverely limits the volume high oxygen gas any one facility can accept.Other conventional oxygen removal techniques, including, for example,catalytic deoxygenation methods, are often limited by expensivecatalysts, high operating temperatures and/or pressures, and/orsignificant downtime resulting from production outages required tomanage catalyst regeneration or replacement. As a result, many producerslimit production and/or intake of high-oxygen natural gas, which leavesa significant natural gas resource under utilized.

Thus, a need exists for an effective, convenient, and relativelyinexpensive system and method for removing oxygen from a natural gasstream. The system should be operationally flexible and efficient andshould also be capable of large scale implementation in both new andexisting facilities. Ideally, the system would minimize capital andoperating expenses while maximizing production in terms of boththroughput and days on stream.

SUMMARY

Some embodiments of the present invention concerns a process forremoving oxygen from a natural gas stream, the process comprising: (a)combining an oxygen-containing natural gas stream with a reducing agentto form a combined gas stream; and (b) contacting at least a portion ofthe combined gas stream with at least one copper-containing catalyst ina deoxygenation zone to thereby provide an oxygen-depleted gas stream,wherein the contacting is carried out under conditions sufficient tomaintain at least a portion of the copper of the copper-containingcatalyst in a reduced state during the contacting.

Another embodiment of the present invention concerns a process forremoving oxygen from a natural gas stream, the process comprising: (a)introducing oxygen-containing natural gas and hydrogen into adeoxygenation zone, wherein the hydrogen is present in the deoxygenationzone in a non-stoichiometric amount relative to the amount of oxygenpresent in the deoxygenation zone; and (b) removing at least a portionof the oxygen from the natural gas with at least one catalyst in thedeoxygenation zone to thereby provide an oxygen-depleted natural gasstream, wherein the average temperature of the deoxygenation zone isless than about 480° F.

Yet another embodiment of the present invention concerns a method forcontrolling a process for removing oxygen from a gas stream, the methodcomprising the steps of (a) combining an oxygen-containing feed gasstream with a hydrogen stream to thereby provide a combined feed gasstream; (b) passing at least a portion of the combined feed gas streamthrough a deoxygenation zone, wherein the passing comprises contactingthe combined feed gas stream with at least one catalyst to remove atleast a portion of the oxygen from the combined feed gas stream andprovide an oxygen-depleted gas stream; (c) measuring a value for atleast one parameter of the oxygen-depleted gas stream; (d) comparing themeasured value for the parameter of the oxygen-depleted gas streamdetermined in step (c) with a target value for the parameter of theoxygen-depleted gas stream to determine a difference; and (e) based onthe difference, controlling at least one parameter of the combined gasstream in order to minimize the difference.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention are described in detailbelow with reference to the attached drawing figures, wherein:

FIG. 1 is a schematic depiction of a natural gas process facilityconfigured according to some embodiments of the present invention,particularly illustrating the use of hydrogen injection to control theoxygen content of a natural gas stream;

FIG. 2 is a schematic depiction of a deoxygenation zone configuredaccording to some embodiments of the present invention, particularlyillustrating certain aspects of a method of controlling thedeoxygenation process; and

FIG. 3 is a flowchart representing the major steps involved in a methodfor controlling a deoxygenation process according to some embodiments ofthe present invention, particularly useful for controlling thedeoxygenation zone schematically depicted in FIG. 2.

DETAILED DESCRIPTION

Turning initially to FIG. 1, a gas processing facility 10 configuredaccording to one or more embodiments of the present invention isprovided. Gas processing facility 10 is illustrated as generallycomprising a sulfur removal zone 20, a deoxygenation zone 30, and aproduct treatment zone 40. Product treatment zone 40 can include one ormore processes used to treat the deoxygenated gas stream and, in someembodiments shown in FIG. 1, may include, for example, at least onecomponent removal zone 50 and/or at least one product purification zone60.

In operation, a feed gas stream in conduit 110 introduced into gasprocessing facility 10 may first be passed through sulfur removal zone20 in order to remove one or more sulfur-containing compounds.Thereafter, the resulting desulfurized stream in conduit 112 can becombined with a reducing agent via conduit 114 a prior to, and/or with areducing agent in conduit 114 b simultaneous with, its introduction intodeoxygenation zone 30. Once in deoxygenation zone 30, theoxygen-containing gas stream, in combination with the reducing agent,may contact at least one catalyst composition under conditionssufficient to remove at least a portion of the oxygen present in the gasstream introduced into deoxygenation zone 30. The resultingoxygen-depleted gas stream in conduit 118 may optionally be routed forfurther separation and/or processing in a product treatment zone 40,which, as shown in the embodiment depicted in FIG. 1, can include atleast one component removal zone 50 and/or at least one productpurification zone 60.

In one embodiment, the feed gas stream introduced into gas processingfacility 10 via conduit 110 may originate from any suitable feed gassource (not shown), such as, for example, an upstream processing unit orfacility, a natural source, or any other suitable gas source. In someembodiments, the feed gas stream in conduit 110 may originate from anatural source, such as, for example, a subterranean oil and gasformation. Optionally, the gas stream in conduit 110 may have undergoneone or more pre-processing steps, such as, for example, separation,drying, or other processing step (not shown) prior to being introducedinto gas processing facility 10 via conduit 110.

The feed gas stream in conduit 110 can comprise a mixture of one or moredifferent components, and may, in some embodiments, include one or morehydrocarbons. When the feed gas stream in conduit 110 is ahydrocarbon-containing gas stream, it can comprise at least about 1, atleast about 2, at least about 5, at least about 10, at least about 25,at least about 30, at least about 40, at least about 50 and/or not morethan about 99, not more than about 97, not more than about 95, not morethan about 90, not more than about 85, not more than about 75 molepercent of one or more hydrocarbon components, based on the total molesof the hydrocarbon-containing gas stream.

In some embodiments, the feed gas stream in conduit 110 can be a naturalgas stream. As used herein, the term “natural gas stream” refers to ahydrocarbon-containing stream including hydrocarbons having six or lesscarbon atoms per molecule. In some embodiments, the feed gas stream inconduit 110 at least about 40, at least about 50, at least about 60, atleast about 75 mole percent and/or not more than about 99, not more thanabout 95, not more than about 85 mole percent of one or morehydrocarbons having six or less carbon atoms per molecule. Examples ofhydrocarbons present in a natural gas feed stream can include, but arenot limited to, methane, ethane, ethylene, propane, propylene, butane,butene, pentane, pentene, hexane, and hexene, and isomers thereof, andcombinations thereof. Further, some embodiments, the feed gas stream inconduit 110 may include less than about 30, less than about 25, lessthan about 20, less than about 10, less than about 5, or less than about1 mole percent of hydrocarbon components having more than six carbonatoms per molecule. In some embodiments, the feed gas stream may notcomprise naphtha, gasoline, or other petroleum cuts that have normalboiling points heavier than naphtha and gasoline.

When the feed gas stream in conduit 110 comprises a natural gas feedstream, a large portion of the hydrocarbons present in the stream may behydrocarbons having three or less carbon atoms per molecule. Inparticular, in some embodiments, the feed gas stream may include atleast about 40, at least about 50, at least about 60, at least about 75mole percent and/or not more than about 99, not more than about 95, notmore than about 90, not more than about 85 mole percent of hydrocarbonshaving three or less carbon atoms per molecule. Additionally, in otherembodiments, the feed gas stream in conduit 110 may also include methanein an amount of at least about 40, at least about 50, at least about 60,at least about 70, at least about 80, at least about 90 mole percent,based on the total moles of hydrocarbon present in the feed gas stream.In some embodiments, methane may be present in an amount of at leastabout 25, at least about 30, at least about 35, at least about 40, atleast about 45, at least about 50, at least about 55, at least about 60,at least about 65, at least about 75 mole percent, based on the totalmoles of the feed gas stream. In the same or other embodiments, the feedgas stream in conduit 110 can have an average energy content of at leastabout 500, at least about 650, at least about 750, at least about 850,at least about 950 BTU/ft³ and/or not more than about 4500, not morethan about 4000, not more than about 3000, not more than about 2500, notmore than about 2000, not more than about 1500 BTU/ft³.

In addition, the feed gas stream may also include minor amounts of othernon-hydrocarbon components, such as, for example, inert gas components.Examples of inert gas components can include, but are not limited to,nitrogen, neon, xenon, argon, helium, krypton, radon, and combinationsthereof. According to some embodiments, the feed gas stream in conduit110 can comprise less than about 10, less than about 5, less than about2, less than about 1, or less than about 0.5 mole percent of one or moreof the inert gas components listed above. For example, in someembodiments, the feed gas stream in conduit 110 can comprise less thanabout 5, less than about 2, less than about 1, or less than about 0.5mole percent of one or more inert gases selected from the groupconsisting of neon, xenon, argon, helium, krypton, radon, andcombinations thereof, while in the same or another embodiment, the feedgas stream may include less than about 10, less than about 8, less thanabout 6, less than about 4, less than about 2, or less than about 1 molepercent of nitrogen and/or helium. According to some embodiments, thefeed gas stream in conduit 110 may not be an inert gas stream and it mayinclude no, or substantially no, inert gas components.

The feed gas stream in conduit 110 may also include small amounts of oneor more combustion products, such as, for example, carbon monoxide (CO),carbon dioxide (CO₂), nitrogen oxides (NO_(x)), sulfur oxides (SO_(x)),and combinations thereof. According to some embodiments, the feed gasstream in conduit 110 can include less than about 2, less than about 1,less than about 0.5, or less than about 0.25 mole percent of one or morecombustion products listed above, based on the total moles of the feedgas steam. In the same or other embodiments, the feed gas stream inconduit 110 may comprise less than about 2000, less than about 1500,less than about 1000, less than about 500 parts per million by weight(ppmw) of CO and/or CO₂, based on the total weight of the feed gasstream. Depending, in part, on the source of the feed gas stream inconduit 110, the feed gas stream may, in some embodiments, include no,or substantially no, combustion products.

The feed gas stream in conduit 110 can also comprise water. In someembodiments, the feed gas stream in conduit 110 can comprise at leastabout 50, at least about 100, at least about 250, at least about 500parts per million by weight (ppmw) and/or not more than about 0.5 weightpercent, not more than about 0.1 weight percent, not more than about5000, or not more than about 1000 ppmw of water based on the totalweight of feed gas stream in conduit 110. Where the water content of thefeed gas exceeds one or more of the upper limits provided above, gasprocessing facility 110 can further comprise an upstream drying zone(not shown in FIG. 1) for removing at least a portion of the water fromthe incoming stream. The drying zone, when present, may include physicalseparation devices, such as vapor-liquid separators, for removing largevolumes of water from the inlet gas and/or it may include one or moredrying vessels employing mole sieve or other solid desiccant forcontacting the feed gas and removing water from the stream in conduit110.

In some embodiments, the feed gas stream in conduit 110 may also includeone or more sulfur-containing components including, for example, organicand/or inorganic sulfur-containing compounds. Examples ofsulfur-containing compounds that may be present in the feed gas streamin conduit 110 include, but are not limited to, hydrogen sulfide (H₂S),carbonyl sulfide (COS), carbon disulfide (CS₂), mercaptans (R—SH),organic sulfides (R—S—R), organic disulfide (R—S—S—R), and combinationsthereof. The amount and/or type of sulfur present in the feed gas streammay depend, at least in part, on the source of the feed gas stream andon any upstream processing to which the stream may have been subjected.In some embodiments, the feed gas stream in conduit 110 can include lessthan about 5, less than about 2, less than about 1, or less than about0.5 mole percent of one or more sulfur-containing compounds, based onthe total moles of the feed gas stream.

When the feed gas stream in conduit 110 includes a sufficient amount ofone or more sulfur-containing compounds, it may be desirable to treatthe feed gas stream in conduit 110 to remove at least a portion of thesulfur-containing compounds in sulfur removal zone 20 prior tointroduction of the stream into deoxygenation zone 30, as generallyillustrated in some embodiments depicted in FIG. 1. Sulfur removal zone20 illustrated in FIG. 1 can comprise any process or unit capable ofremoving at least a portion of one or more sulfur-containing compoundsfrom the feed gas stream in conduit 110. In some embodiments, sulfurremoval zone 20 may be configured to reduce the amount of sulfur in thefeed gas stream by at least about 10, at least about 20, at least about30, at least about 40, at least about 50, at least about 60 percent,based on the total amount of sulfur originally present in the feed gasstream introduced into sulfur removal zone 20 via conduit 110.Optionally, at least a portion of the sulfur removal process utilized insulfur removal zone 20 can be carried out in the presence of hydrogen,which can be added via conduit 111 as shown in FIG. 1. When used,hydrogen may be present in an amount of at least about 500, at leastabout 750, at least about 1000 parts per million by volume (ppmv),and/or not more than about 5000, not more than about 2500, not more thanabout 1500 ppmv.

Sulfur removal zone 20 can include any suitable type of sulfur removalprocess or treatment step. In some embodiments, sulfur removal zone 20may employ a liquid solvent, such as an amine or caustic, for contactingthe incoming gas stream in a column or washer. In the same or anotherembodiment, sulfur removal zone 20 can employ at least one solid sulfurremoval compound, such as an adsorbent, utilized in one or more fixed ormoving bed vessels. As used herein, the term “adsorbent” is not limitedto material capable of chemically and/or physically adsorbing one ormore sulfur-containing compounds, but is also intended to encompassmaterials that catalyze and/or absorb sulfur-containing materials. Whenthe adsorbent material present in sulfur removal zone 20 includes asolid support, it may optionally be promoted with at least onedesulfurization metal supported on, in, and/or within at least a portionof the support material. The support material can comprise a porousmaterial such as, for example, alumina, zinc, silica, and combinationsthereof. In some embodiments, the support material can comprise zincoxide.

When the adsorbent material is promoted with at least onedesulfurization metal, the metal can comprise any metal capable ofchemically reacting or coordinating with one or more types ofsulfur-containing compounds. Examples of suitable desulfurization metalscan include, but are not limited to, nickel, cobalt, molybdenum, copper,silver, ruthenium, rhodium, palladium, tungsten, manganese, chromium,and combinations thereof. When utilized, the desulfurization metal canbe present in the adsorbent material in an amount of at least about 0.5,at least about 1, at least about 2 weight percent and/or not more thanabout 8, not more than about 6, not more than about 5 weight percent,based on the total weight of the absorbent material. When the adsorbentincludes two or more desulfurization metals, the total weight of bothmetals may fall in the ranges above, while the amount of each individualmetal may be at least about 0.25, at least about 0.5, at least about 1and/or not more than about 5, not more than about 4, not more than about2.5, not more than about 1.5 weight percent, based on the total weightof the adsorbent material. In some embodiments, the adsorbent cancomprise a copper-promoted zinc oxide adsorbent.

In some embodiments, sulfur removal zone 20 may further include one ormore other types of processes or treatment steps capable of removing oneor more other types of compounds from the incoming gas stream. Forexample, in some embodiments, gas processing facility 10 may alsoinclude one or more treatment zones located upstream of sulfur removalzone 20 for removing inorganic or organic silicon materials and/orparticulates. In some embodiments, such treatment zones can include oneor more beds of materials such as activated alumina, which, in additionto removing silicon materials, may also be capable of converting atleast a portion of one or more sulfur-containing compounds into othersulfur-containing compounds which are more easily removed within sulfurremoval zone 20. Additionally, as discussed previously, gas processingfacility 10 may also include one or more drying zones located before orafter sulfur removal zone 20 to reduce the level of water in the feedgas stream to an amount in the ranges described previously.

Further, sulfur removal zone 20 may, if needed, also include one or moremoisture removal or drying zones to reduce the level of water in thefeed gas stream to an amount within the ranges provided previously.

Sulfur removal zone 20 can be operated under conditions sufficient toremove at least a portion of one or more sulfur-containing compoundsfrom the feed gas stream in conduit 110. In some embodiments, thedesulfurization processes or steps conducted within sulfur removal zone20 may be carried out at an average temperature of at least about 40°F., at least about 75° F., at least about 100° F., at least about 150°F., at least about 200° F., at least about 250° F., at least about 300°F., at least about 350° F. and/or not more than about 800° F., not morethan about 700° F., not more than about 650° F., not more than about600° F. The pressure of the feed gas stream being treated in sulfurremoval zone 20 may also vary, but, in some embodiments, can be at leastabout 100, at least about 200, at least about 300, at least about 500,at least about 600, at least about 750, at least about 850, at leastabout 900, and/or not more than about 2500, not more than about 2000,not more than about 1500, not more than about 1000, not more than about750 psi.

Referring again to FIG. 1, the desulfurized gas stream in conduit 112exiting sulfur removal zone 20 can comprise less than about 100, lessthan about 75, or less than about 50, less than about 25, less thanabout 15, less than about 10, or less than about 1 ppmv of one or moresulfur-containing components. In some embodiments, the desulfurized gasstream in conduit 116 can have a total sulfur content of at least about1, at least about 2, at least about 5, at least about 10 and/or not morethan about 40, not more than about 25, not more than about 20, not morethan about 10 ppmv, based on the total volume of the desulfurized feedgas stream in conduit 112. This may represent, in some embodiments, atotal sulfur removal efficiency of at least about 50, at least about 60,at least about 70, at least about 80, at least about 90 percent, basedon the total amount of sulfur originally present in the feed gas streamin conduit 110. As used herein, the term “sulfur removal efficiency”refers to the difference between the total sulfur content of thedesulfurized feed gas stream in conduit 112 and the total sulfur contentof the feed gas stream in conduit 110, expressed as a percentage of thetotal sulfur content of the feed gas stream in conduit 110. In oneembodiment, the desulfurized gas stream in conduit 112 can comprise lessthan about 20, less than about 15, less than about 10, less than about 5percent of the total amount of sulfur originally present in the feed gasstream in conduit 110, based on the total amount, by weight, of sulfurpresent in the feed gas stream in conduit 110.

As shown in FIG. 1, the desulfurized gas stream in conduit 116 maysubsequently be routed to a deoxygenation zone 30. In some embodiments,the desulfurized gas stream in conduit 112 can have a total oxygencontent of at least about 20, at least about 50, at least about 100, atleast about 200, at least about 300, at least about 500, at least about750, at least about 1000 ppmv and/or not more than about 15,000, notmore than about 12,500, not more than about 10,000, not more than about7500, not more than about 5000, not more than about 2500 ppmv, based onthe total volume of the stream in conduit 112. In some embodiments, thismay be the same as, or may be slightly lower than, the total oxygencontent of the feed gas stream introduced into gas processing facility10 via conduit 110. Accordingly, in some embodiments, sulfur removalzone 20 may not remove any substantial amount of oxygen from the feedgas stream, such that the oxygen content of the feed gas stream inconduit 110 is within about 50, within about 40, within about 30, withinabout 20, within about 10, or within about 5 percent of the total amountof oxygen in the desulfurized feed gas stream in conduit 112.

As shown in one embodiment depicted in FIG. 1, at least a portion of thedesulfurized, but oxygen-containing feed gas stream in conduit 112 canoptionally be combined with a reducing agent via conduit 114 a tothereby provide a combined gas stream in conduit 116. Alternatively, orin addition, all or a portion of the reducing agent can be combined withthe desulfurized feed gas stream within deoxygenation zone 30, as shownconduit 114 b. In some embodiments, the reducing agent can comprisehydrogen and, in the same or other embodiments, the reducing agent canbe a hydrogen-containing gas stream comprising at least about 50, atleast about 65, at least about 75, at least about 85, at least about 90,at least about 95 weight percent hydrogen, based on the total weight ofthe stream. The hydrogen may originate from any suitable source and, insome embodiments, may originate from other areas within or external togas processing facility 10.

According to some embodiments, the hydrogen (or other reducing agent,when used) combined with the oxygen-containing gas stream in conduit 116may be present in the combined gas stream in a non-stoichiometric amountas compared to the amount of oxygen present in the combined stream. Asused herein, the term “non-stoichiometric” refers to an amount ofhydrogen other than the amount required to exactly react with the oxygenaccording to the following chemical equation: 2H₂+O₂->2H₂O. Amounts ofhydrogen that exceed or fall short of the stoichiometric amount ofhydrogen in the oxygen-containing gas stream are each considered to be“non-stoichiometric,” as described herein. In some embodiments, theamount of hydrogen present in the combined gas stream in conduit 116and/or within deoxygenation zone 30 may be at least about 40, at leastabout 50, at least about 60, at least about 70, at least about 80, atleast about 85, at least about 90, at least about 95 and/or not morethan about 200, not more than about 175, not more than about 150, notmore than about 125, not more than about 115, not more than about 110,not more than about 105 percent of stoichiometric.

When hydrogen is present in the combined gas feed stream in conduit 116in a non-stoichiometric amount, the molar ratio of hydrogen to oxygen inthe combined gas stream in conduit 116 may not be 2:1. In someembodiments, hydrogen may be present in a sub-stoichiometric amount(i.e., the oxygen may be present in a stoichiometric excess) such thatthe molar ratio of hydrogen to oxygen in the combined gas stream may beless than 2:1, less than about 1.99:1, less than about 1.95:1, less thanabout 1.90:1, less than about 1.85:1. In other embodiments, hydrogen maybe present in a stoichiometric excess so that the molar ratio ofhydrogen to oxygen in the combined stream is at least about 2:01:1, atleast about 2.05:1, at least about 2.10:1, or at least about 2.15:1.When all or part of the hydrogen (or other reducing agent) is added tothe oxygen-containing feed gas stream within deoxygenation zone 20 viaconduit 114 b, the molar ratio of the total amount of hydrogen to thetotal amount of oxygen within desulfurization zone 20 may also fallwithin one or more of the ranges described above. Specific methods forcontrolling the amount of hydrogen added to the feed gas stream will bediscussed in detail shortly.

Turning again to FIG. 1, the gas stream in conduit 116, which mayoptionally be a combined gas feed stream including hydrogen or otherreducing agent introduced via conduit 114 a, can then be routed intodeoxygenation zone 30, wherein at least a portion of the gas stream canbe contacted with at least one catalyst composition under conditionssufficient to remove at least a portion of the oxygen from the gasstream and provide an oxygen-depleted gas stream in conduit 118. In someembodiments, the contacting can be carried out under conditionssufficient to remove at least about 80, at least about 90, at leastabout 95, at least about 97, at least about 99, at least about 99.5percent of the total amount of oxygen introduced into deoxygenation zone30 via conduit 116, based on the total amount of oxygen originallypresent in the gas stream in conduit 116. Accordingly, theoxygen-depleted gas stream withdrawn from deoxygenation zone 30 viaconduit 118 can comprise less than about 20, less than about 10, lessthan about 5, less than about 2, less than about 1, less than about 0.5percent of the total amount of oxygen originally introduced intodeoxygenation zone 30 in the oxygen-containing feed gas stream inconduit 116.

The catalyst composition used to contact the feed gas stream introducedinto deoxygenation zone 30 in conduit 116 can comprise at least onesupport and one or more catalytic metals. In some embodiments, thecatalytic metal or metals may be impregnated onto at least a portion ofthe support material, while, in other embodiments, the catalytic metalor metals may be at least partially dispersed throughout the supportmaterial matrix. The support material of the catalyst composition cancomprise material capable of withstanding the operating conditionswithin deoxygenation removal zone 30 while providing sufficient supportand porosity to facilitate the necessary deoxygenation reactions. Insome embodiments, the support material can be selected from the groupconsisting of silica, alumina, zinc oxide, and combinations thereof.

The catalytic metal employed by the deoxygenation catalyst compositionin deoxygenation zone 30 can comprise any metal capable of facilitatingremoval of at least a portion of the oxygen from the incoming gasstream. In some embodiments, the catalytic metal used in deoxygenationzone 30 can be selected from the group consisting of copper, platinum,palladium and combinations thereof. In other embodiments, the catalyticmetal can comprise copper. The amount of catalytic metal present withinthe catalyst composition may vary but, in some embodiments, may be atleast about 1, at least about 2, at least about 2.5, at least about 3and/or not more than about 20, not more than about 15, not more thanabout 10, not more than about 8, not more than about 6, not more thanabout 5 weight percent, based on the total weight of the catalystcomposition. In other embodiments, the catalytic metal can be present inthe catalyst composition in an amount of at least about 10, at leastabout 15, at least about 20, at least about 30 and/or not more thanabout 70, not more than about 65, not more than about 60, not more thanabout 50 weight percent, based on the total weight of the catalystcomposition. In part, the amount of catalytic metal present may beimpacted by the distribution of the catalytic metal over or within thesupport material.

According to some embodiments, the step of contacting theoxygen-containing feed gas stream with the catalyst composition may becarried out such that at least a portion of the catalytic metal remainsin a reduced state during all, or substantially all, of the contactingstep. This is contrary to many conventional deoxygenation processes,which permit an increasing amount of catalyst to become oxidized (i.e.,a decreasing amount of catalyst in a reduced state) as oxygen is removedfrom the feed gas stream. In part, addition of hydrogen into thecombined gas stream in conduit 116 and/or addition of hydrogen todeoxygenation zone 30 during the contacting step may help facilitateon-line reduction of at least a portion of the catalyst metal during thedeoxygenation process. Although not wishing to be bound by theory, it isbelieved that, as the catalytic metal becomes oxidized during oxygenremoval from the gas stream, at least a portion of the injected hydrogenmay facilitate immediate or near immediate reduction of at least aportion of the oxidized catalyst, thereby retaining at least a portionof the catalytic metal in a reduced state. According to some embodimentsof the present invention, at least about 10, at least about 20, at leastabout 30, at least about 40, at least about 50, at least about 60, atleast about 70, at least about 80, at least about 90 percent of thetotal amount of catalytic metal of the catalyst composition remains in areduced state during contacting. In one embodiment, less than about 30,less than about 20, less than about 10, or less than about 5 percent ofthe total amount of catalytic metal of the catalyst composition remainsin an oxidized state during the contacting step.

In order to facilitate reduction of the catalytic metal within thedeoxygenation zone while simultaneously removing oxygen from the feedgas stream, the temperature of deoxygenation zone 30 during contactingcan be maintained at temperature of at least about 325° F., at leastabout 330° F., at least about 340° F., at least about 345° F., at leastabout 350° F., at least about 355° F., at least about 360° F., at leastabout 365° F., at least about 370° F., at least about 375° F., at leastabout 380° F., at least about 385° F., at least about 390° F., at leastabout 395° F., at least about 400° F. and/or not more than about 480°F., at least about 475° F., at least about 470° F., at least about 465°F., at least about 460° F., at least about 455° F., at least about 450°F., at least about 445° F., at least about 440° F., at least about 435°F., at least about 430° F., at least about 425° F. The contacting stepmay be carried out at a temperature in the range of from about 325° F.to about 480° F., about 340° F. to about 460° F., about 350° F. to about450° F., or about 400° F. to about 425° F. The total pressure withindeoxygenation zone 30 can be at least about 500, at least about 600, atleast about 750, at least about 850, at least about 900 pounds persquare inch (psi) and/or not more than about 2500, not more than about2250, not more than about 2000, not more than about 1750, not more thanabout 1500 psi. In some embodiments, the desulfurized gas stream inconduit 112 and/or the combined gas stream in conduit 116 may be heatedand/or compressed as needed in order to achieve the desired temperatureand/or pressure for the contacting step.

The deoxygenation catalyst composition employed in deoxygenation zone 30may be in any suitable form and can, in some embodiments, be arranged inone or more fixed bed reactors located within deoxygenation zone 30.According to some embodiments, deoxygenation zone 30 may include two ormore fixed bed reactors arranged in series, such that the deoxygenatedgas stream from the first, or lead, bed can be used as the feed streamto the second, or lag, bed. In another embodiment, deoxygenation zone 30may include two fixed bed reactors arranged in parallel, such that onereactor can be configured to receive and contact the feed gas streamwith the catalyst composition, while the other reactor is off line andis not receiving a feed gas stream. In addition to including thedeoxygenation catalyst composition described above, one or more reactorsutilized in deoxygenation zone 30 can include additional catalyst orsorbent materials located before, after, or amongst the deoxygenationcatalyst to help remove one or more other components of the gas streamincluding, for example, sulfur-containing compounds and/or water.

In some embodiments of the present invention, the amount of hydrogenintroduced into feed stream in conduit 112 and/or into desulfurizationzone 30 can be adjusted during at least a portion of the contacting stepcarried out in desulfurization zone 30 in order to achieve a desiredlevel of oxygen removal. According to some embodiments, at least aportion of the adjusting may be carried out to maintain the molar ratioof hydrogen to oxygen in the oxygen-containing feed gas stream inconduit 116 within about 10, within about 5, within about 2, or withinabout 1 percent of a controlled set point, which may fall within one ormore of the ranges provided above. For example, in some embodiments, thecontrolled set point of the hydrogen to oxygen ratio in the feed streamin conduit 116 can be at least about 1.80:1, at least about 1.85:1, atleast about 1.90:1 at least about 1.95:1 and/or not more than about2.2:1, not more than about 2.15:1, not more than about 2.10:1, not morethan about 2.05:1, not more than about 2.01:1.

According to some embodiments, at least a portion of the adjusting canbe carried out to maintain the amount of hydrogen present in theoxygen-depleted stream exiting deoxygenation zone 30 via conduit 118above a maximum upper threshold limit and/or below a minimum lowerthreshold limit. In the same or other embodiments, the adjusting of thehydrogen-to-oxygen ratio in the feed gas in conduit 116 can be carriedout to maintain the amount of oxygen in the oxygen-depleted gas steam inconduit 118 above a maximum upper threshold limit and/or below a minimumlower threshold limit. In addition to adjusting amount of hydrogenintroduced into the feed stream in conduit 116, the temperature of thefeed stream and/or the overall flow rate of the combined feed gas streamin conduit 116 may also be adjusted in order to control the degree ofoxygen removal achieved in deoxygenation zone 30. Specific embodimentsof methods for controlling the operation of a deoxygenation reactorwithin deoxygenation zone 30 will now be discussed in further detailwith reference to FIGS. 2 and 3.

Turning now to FIG. 2, one embodiment of a deoxygenation reactor 230suitable for use in deoxygenation zone 30 of FIG. 1 is shown.Additionally, FIG. 3 provides a flow chart outlining the major steps ofa method 300 of controlling a deoxygenation reactor including, forexample, deoxygenation reactor 230 shown in FIG. 2. As shown by theembodiment of deoxygenation reactor 230 depicted in FIG. 2, anoxygen-containing feed gas stream in conduit 210 can be combined withhydrogen (or other reducing agent) in conduit 214, and the combined gasstream in conduit 216 can be introduced into a bed of deoxygenationcatalyst 222 within deoxygenation reactor 230. The resultingoxygen-depleted gas stream in conduit 216 can then be withdrawn from anupper portion of deoxygenation reactor 230 and sent to furtherdownstream processing, transportation, and/or storage.

As shown in FIG. 3, the first step 310 of method 300 for controlling theoxygen removal process carried out in the system of FIG. 2, is todetermine a value for at least one parameter of the oxygen-depleted gasstream in conduit 218. Examples of parameters to be determined caninclude, for example, oxygen content of the oxygen-depleted gas stream,the hydrogen content of in the oxygen-depleted gas stream, the pH of theoxygen-depleted feed gas stream, and combinations thereof. Suchparameters can be measured using, for example, on-line analyzers such ason-line pH analyzer 252 and on-line hydrogen and/or oxygen analyzer 254shown in FIG. 2. Additionally, other methods of determining theseparameters, such as, for example pH paper or hand-held gas monitoringdevices such as DRAEGER tubes may also be used alone, or in combinationwith online measurements.

Once a value for a parameter of the oxygen-depleted gas stream has beendetermined, the measured value can be compared with a target value forthat parameter to determine a difference, as represented by step 320 inFIG. 3. Subsequently, as shown by step 330, based on the difference, atleast one of the parameters of the oxygen-containing feed gas stream inconduit 116 can be controlled in order to minimize the differencebetween the measured and target values for the selected parameter of theoxygen-depleted stream. Examples of parameters of the oxygen-containingfeed gas stream that may be controlled can include, for example, themolar ratio of hydrogen to oxygen in the combined oxygen-containing gasstream, the temperature of the combined gas stream, or both the molarratio of hydrogen to oxygen and the temperature of the combined gasstream. When the parameter of the oxygen-containing feed gas streamselected is the molar ratio of hydrogen to oxygen in the combinedoxygen-containing gas stream, this parameter may be controlled byadjusting the amount of hydrogen injected into the oxygen-containingfeed gas stream in conduit 210. Alternatively, or in addition, thisparameter may also be controlled by adjusting the amount of oxygen inand/or the flow rate of the feed gas stream in conduit 210, although thelatter may be more desirable from a practical standpoint.

The target value itself and how the one or more feed stream parametersare controlled to minimize the difference between the measured value andthe target value can be dependent, at least in part, on the amount ofhydrogen and oxygen in the combined oxygen-containing feed gas stream inconduit 216. The feed stream parameters may be controlled to maintain anon-stoichiometric ratio of hydrogen to oxygen, although the particulartarget values and methods of adjusting the feed gas parameters maydepend on whether the combined oxygen-containing feed gas streamintroduced into deoxygenation reactor 230 has a stoichiometric excess ofhydrogen (i.e., a sub-stoichiometric amount of oxygen) or asub-stoichiometric amount of hydrogen (i.e., a stoichiometric excess ofoxygen). Specific examples of target values for the parameters of theoxygen-depleted gas stream, as well as methods of controlling theselected parameter of the oxygen-containing feed gas stream, for each ofthese situations will now be discussed in greater detail below.

According to some embodiments of the present invention, theoxygen-containing feed gas stream in conduit 216 shown in FIG. 2 canhave a non-stoichiometric molar ratio of hydrogen to oxygen such thatthe hydrogen is present in the oxygen-containing feed gas stream in asub-stoichiometric amount. According to one embodiment, the molar ratioof hydrogen to oxygen in the combined oxygen-containing stream inconduit 216 may be less than 2:1 and can be, for example, within one ormore of the ranges described above with respect to the combined feedstream in conduit 218 of FIG. 2 measured in step 310 of method 300depicted in FIG. 3. The parameter of the oxygen-depleted gas stream inconduit 216 of FIG. 2 may be the total oxygen content and the targetvalue used for comparison to the measured value in step 320 may be amaximum oxygen limit and/or a minimum oxygen limit. When the targetvalue is a maximum oxygen limit, the target value may be not more thanabout 25, not more than about 20, not more than about 15, not more thanabout 10, not more than about 5, not more than about 2 ppmw of oxygen,based on the total volume of the weight of the oxygen-depleted stream.When the target value is a minimum oxygen limit, the target value may beat least about 1, at least about 2, at least about 5 ppmw of oxygen,based on the total weight of the oxygen-depleted gas stream. Becausehydrogen is introduced into deoxygenation reactor 230 in asub-stoichiometric amount, the hydrogen content of the oxygen-depletedgas stream may be less than about 10, less than about 5, less than about2, or less than about 1 ppmw, based on the total weight of theoxygen-depleted stream in conduit 218. In some embodiments, theoxygen-depleted stream in conduit 218 may comprise no hydrogen.

When the parameter of the oxygen-depleted gas stream in conduit 218measured in step 310 includes total oxygen content, the oxygen contentcan be determined by using, for example, on-line analyzer 254 shown inFIG. 2. Once a value for the parameter has been measured, the measuredvalue may be transmitted by, for example, a signal, shown in FIG. 2 asdashed line 280, to a control system 250, wherein it may be comparedwith a target value for oxygen content that is introduced into controlsystem 250 by another signal represented by dashed line 282. The targetvalue may be directly input by a user or it may originate from a setpoint generated from past process information or another source. Oncecontrol system 250 has received both the measured and target values foroxygen content of the oxygen-depleted gas stream in conduit 218 (orother measured parameter), it can compare the measured value to thetarget value to determine a difference.

Once a difference has been determined between the total oxygen contentof the oxygen-depleted gas stream in conduit 218 and the target valueprovided to control system 250, at least one of the parameters of thecombined feed stream in conduit 216 can be adjusted or controlled, asshown by step 330 of method 300. When the parameter of oxygen-depletedgas stream 218 measured in step 310 is the total oxygen content of theoxygen-depleted gas stream and the target value is a minimum oxygencontent, the parameter of the combined feed gas stream controlled instep 330 can be the amount of hydrogen introduced into the feed gasstream in conduit 110. For example, if the difference between themeasured oxygen content and the minimum target value is negative (i.e.,the measured value is less than the minimum target value), then thedifference can be minimized by reducing the amount of hydrogen inconduit 214 combined with the feed gas stream in conduit 210 by, forexample, closing valve 258 shown in FIG. 2.

In the same or another embodiment, the target value compared to themeasured oxygen content of the oxygen-depleted gas stream can be amaximum oxygen content. According to this embodiment, the controllingstep 330 depicted in FIG. 3 can include adjusting the amount of hydrogenintroduced into and/or the temperature of the feed gas stream in conduit210. For example, when the difference between the measured oxygencontent and the target value for maximum oxygen content in theoxygen-depleted gas stream in conduit 218 is positive (i.e., themeasured value exceeds the target value), the controlling step 330 ofmethod 300 may include increasing the amount of hydrogen added to thecombined feed gas stream in conduit 216 by, for example, opening valve258 shown in FIG. 2.

Additionally, or in the alternative, when difference between themeasured oxygen content and the maximum oxygen content is positive(i.e., when the measured value exceeds the target value), thetemperature of the combined gas stream in conduit 216 can also beincreased to affect a reduction in the amount of oxygen in theoxygen-depleted gas stream in conduit 218. The use of feed gastemperature to control the oxygen content of the oxygen-depleted steamin conduit 218 can be used as needed, optionally in combination with thestep of adjusting the amount of hydrogen added to the feed gas stream,until the temperature of the feed gas stream approaches a temperature ofat least about 425° F., at least about 435° F., at least about 445° F.,or at least about 450° F.

When the temperature of the feed gas stream in conduit 216 exceeds atemperature of approximately 450° F. and the measured oxygen content ofthe oxygen-depleted gas stream in conduit 218 exceeds the target valuefor maximum oxygen content, the catalyst composition in deoxygenationreactor 230 may require further reduction and/or replacement. Accordingto the present invention, replacement and/or reduction of the catalystmay be due, at least in part, to poisoning of the catalyst by othercontaminants, such as sulfur-containing compounds. Unlike manyconventional deoxygenation processes, which require frequent catalystchange outs or treatment steps, the method of operation of the presentinvention substantially eliminates the need to replenish the catalystcomposition due to oxygen-related contamination. If the deoxygenationzone includes only one reactor, the entire zone may need to be shut downduring such a step. However, if deoxygenation zone includes two or morereactors, operated in parallel or series, at least one of the reactorsmay remain on-line and operating while the catalyst in one or more otherreactors is changed out or reduced.

In contrast to conventional processes, the typical time intervalsbetween required reduction or replacement of catalyst 222 ofdeoxygenation reactor 230 can be, for example, at least about 2 months,at least about 4 months, at least about 8 months, at least about 1 yearand/or not more than about 5 years, not more than about 2.5 years, notmore than about 2 years, not more than about 18 months, measured astime-on-stream. In contrast, many conventional deoxygenation processesused to treat similar feed streams have a far lower time-on-stream,sometimes on the order of a month or less.

According to other embodiments of the present invention, hydrogen may bepresent in the oxygen-containing feed gas stream in a stoichiometricexcess. In these embodiments, the molar ratio of hydrogen to oxygen inthe oxygen-containing gas stream in conduit 216 may be greater thanabout 2:1 and can be, for example, within one or more of the rangesdescribed above. According to these embodiments, the parameter of theoxygen-depleted gas stream in conduit 216 measured during step 310 ofmethod 300 may be the total hydrogen content and the target value usedfor comparison in step 320 may be a maximum hydrogen limit and/or aminimum hydrogen limit. When the target value includes a maximumhydrogen limit, the target value for the hydrogen in the oxygen-depletedstream may be not more than about 100, not more than about 75, not morethan about 50, not more than about 25, not more than about 20, not morethan about 10 ppmw, based on the total weight of the oxygen-depletedstream in conduit 218. When the target value for hydrogen content in theoxygen-depleted stream is a minimum hydrogen content, the target valuemay be at least about 1, at least about 2, at least about 5, or at leastabout 10 ppmw, based on the total weight of the stream. In someembodiments, the total oxygen content of stream in conduit 218 may beless than about 20, less than about 15, less than about 10, or less thanabout 5 ppmw, based on the total weight of the stream. In someembodiments, the deoxygenated stream in conduit 218 can comprise nooxygen.

When the parameter of the oxygen-depleted gas stream in conduit 218measured in step 320 of method 300 includes total hydrogen content, thehydrogen content can be determined by using, for example, an on-lineanalyzer 254 shown in FIG. 2. In a similar manner as describedpreviously, a value for the measured parameter may be transmitted bysignal 280 shown in FIG. 2 to control system 250, wherein it may becompared with a target value introduced by another signal 282. Once adifference between the measured and target values has been determined,at least one of the parameters of the combined feed stream in conduit216 can be adjusted, as shown by step 330 of method 300.

When the parameter of oxygen-depleted gas stream 218 measured in step310 is the total hydrogen content and the target value is a minimumhydrogen content, the parameter of the combined feed gas streamcontrolled in step 330 may be the amount of hydrogen introduced into thefeed gas stream in conduit 210. For example, if the difference betweenthe measured hydrogen content and the minimum target value is negative(i.e., the measured value is less than the minimum target value), thenthe difference can be minimized by increasing the amount of hydrogencombined with the feed gas stream in conduit 210 by, for example,opening valve 258. Additionally, or in the alternative, the differencebetween the measured total hydrogen content and a minimum hydrogencontent of the oxygen-depleted gas in conduit 218 can also be minimizedby adjusting the temperature of the combined gas stream in conduit 216.For example, when difference between the measured oxygen content and theminimum hydrogen content is negative (i.e., the measured value is lessthan the minimum target value), the temperature of the combined gasstream in conduit 216 can be increased to affect additional reaction ofthe oxygen in the feed gas stream with the injected hydrogen.

When the measured parameter of the oxygen-depleted gas includes totalhydrogen content, the target value can include a maximum hydrogencontent. According to this embodiment, step 330 depicted in FIG. 3 canalso include adjusting the amount of hydrogen introduced into the feedgas stream in conduit 210. For example, when the difference between themeasured hydrogen content and the target value for maximum hydrogencontent in the oxygen-depleted gas stream in conduit 218 is positive(i.e., the measured value exceeds the target value), step 330 of method300 can include reducing the amount of hydrogen added to the combinedfeed gas stream in conduit 216 by, for example, closing valve 258.Additionally or alternatively, positive differences between the measuredhydrogen content and the maximum hydrogen value can be reduced byreducing the temperature of the feed gas stream in conduit 216.

Additionally, the molar ratio of hydrogen to oxygen in the combined feedgas stream in conduit 216 can also be adjusted by adjusting the flowrate and/or oxygen content of the oxygen-containing feed gas stream inconduit 210. Because the oxygen content of the feed gas stream may bemore difficult to control, increasing or decreasing the flow rate of theoxygen-containing stream in conduit 210 may also be used to adjust themolar ratio of hydrogen to oxygen in the combined feed stream in conduit216 introduced into deoxygenation reactor 230.

In some embodiments, the parameter of the oxygen-depleted gas stream inconduit 218 measured in step 320 of method 300 can be pH, which can bedetermined by using, for example, on-line pH analyzer 252 shown in FIG.2. In a similar manner as previously discussed, the measurement obtainedby on-line pH analyzer 252 can be transmitted to control system 250 viasignal 284 and compared to a target value introduced into control system250 via signal 282. Thereafter, a difference can be determined betweenthe measured and target pH values and one or more parameters of thecombined feed gas stream in conduit 216 can be adjusted to minimize thedifference. When the parameter of the oxygen-depleted gas stream inconduit 218 measured in step 310 is pH and the target value is a minimumpH, the parameter of the combined feed gas stream in conduit 216 to beadjusted in step 320 can be temperature. For example, if the differencebetween the measured pH value and the minimum pH value is negative(i.e., if the measured value is less than the minimum target value), thetemperature of the combined gas stream in conduit 216 can be increased.In some embodiments, the minimum pH of the oxygen-depleted gas stream inconduit 218 can be at least about 5, at least about 5.1, at least about5.25 and/or not more than about 6.5, not more than about 6.0, not morethan about 5.75.

Referring again to FIG. 3, in some embodiments, steps 310 through 330 ofmethod 300 may be repeated one or more times in order to effectivelyminimize the difference between the measured and target values. Thesteps of method 300 may be repeated until the difference between themeasured and target value is not more than about 10, not more than about5, not more than about 2, not more than about 1 percent of the targetvalue. Similarly, method 300 may not even be initiated until thedifference between the measured and target values is at least about 1,at least about 2, at least about 5 percent of the target value. Thesteps of method 300 described according to several embodiments of thepresent invention may be repeated at least 1, at least 2, at least 3and/or not more than about 20, not more than about 10, not more thanabout 5 times. In other embodiments when method 300 is carried out usingcontrol system 250, the method may be carried out on a continuous basis,as needed, when deoxygenation reactor 230 is in operation. Further,although illustrated in FIG. 2 as being carried out by control system250, it is also possible that at least a part, or all, of the steps ofmethod 300 may be performed manually.

Referring back to FIG. 1, the deoxygenated stream 118 withdrawn fromdeoxygenation zone 30 can have a total oxygen content of less than about25, less than about 20, less than about 10, less than about 5 ppmw,based on the total weight of the stream. In some embodiments, theoxygen-depleted gas stream in conduit 118 can comprise at least about 1,at least about 2, at least about 5 ppmw of hydrogen and/or not more thanabout 100, not more than about 75, not more than about 50, not more thanabout 25 ppmw of hydrogen, based on the total weight of the deoxygenatedstream in conduit 118. Additionally, the pH of the deoxygenated streamcan be at least about 5, at least about 5.5, or at least about 6.

As shown in FIG. 1, upon removal from deoxygenation zone 118, theoxygen-depleted gas stream may then be subjected to further separationor purification processes in product separation zone 40. In someembodiments, at least a portion of product separation zone 40 can beoperated under cryogenic conditions and/or may be configured to removeone or more components from the deoxygenated stream, including, forexample nitrogen, helium, C2 and heavier hydrocarbons and the like. Thespecific configuration of columns or processes within product separationzone 40 is not limited and may depend, at least in part, on the type andsource of the feed gas in conduit 110 and the desired products to beprovided via conduit 122 and others (not shown in FIG. 1).

Although described herein with respect to a natural gas stream, itshould also be understood that the processes for removing oxygen and themethod for controlling the oxygen removal processes described above maybe applicable to various other types of feed gas streams, particularlyhydrocarbon-containing feed gas streams having hydrocarbon contentswithin the ranges described previously.

Example

Several trial runs were conducted using a lab-scale deoxygenationreactor to determine the ability of several different catalystcompositions to remove oxygen from a natural gas feed stream. For eachrun, the reactor, which was formed from 6 inch, schedule 80 pipe, wasloaded with upper and lower support beds including ½ inch, ¼ inch, and ⅛inch ceramic support balls arranged in 6-inch layers. Between thesupport beds, the reactor was loaded with 1 cubic foot of catalystmaterial, as described below.

The first trial, Run 1, was conducted by passing oxygen-containingnatural gas having an average flow rate of 0.146 MMSCFD and an averagetemperature of 88° F. through a fixed bed of 2 to 4 mm beads of 0.3weight percent palladium on alumina catalyst. For Run 1, the feed gashad an average oxygen content of 2554 ppm and a hydrogen content of 0.01mole percent. The composition of the oxygen-containing feed gas used inRun 1 is summarized in Table 1, below. Upon passage of the gas throughthe deoxygenation reactor, a sample of the oxygen-depleted gas streamwas withdrawn and its composition determined using ASTM D-5443.Additional detailed component analyses were performed using amulti-isomer analysis by GC and a GC-MS qualitative analysis. Theresults of the compositional analyses are provide in Table 2, below. Asecond trial, Run 2, was carried out on the same reactor system, undersimilar conditions and using a stream of oxygen-containing natural gashaving a similar composition. The actual composition of the feed gasused during Trial 2 is summarized in Table 1 below. During Run 2, thenatural gas feed stream, which had an average flow rate of 0.135 MMSCFDand an average temperature of 65° F., was passed through a fixed bed ofthe same palladium catalyst used during Run 1. Compositions of theproduct gas collected during Run 2 are summarized in Tables 1 and 2,below.

Two additional trial runs, Runs 3 and 4, were both carried out in asimilar manner to Runs 1 and 2 described previously, except the naturalgas was passed through a fixed bed of copper-containing catalystaccording to one embodiment of the present invention. Thecopper-containing catalyst used during Runs 3 and 4 included 3×3 tabletsof 40 percent copper (II) oxide, with the balance of zinc oxide andalumina. During Run 3, the average contacting temperature between thenatural gas stream and the catalyst was at 370° F., while the contactingtemperature during Run 4 was increased to 395° F. The composition of thefeed and product gases for Runs 3 and 4 are also summarized in Tables 1and 2, below.

TABLE 1 Composition of Inlet and Outlet Streams of Deoxygenation Reactorwith Various Catalysts Run 1 Run 2 Run 3 Run 4 Inlet Outlet Change InletOutlet Change Inlet Outlet Change Inlet Outlet Change Component Mole %Mole % Mole % Mole % Mole % Mole % Mole % Mole % Mole % Mole % Mole %Mole % Nitrogen 8.51 9.54 1.03 8.83 9.16 0.33 8.13 7.71 −0.42 8.13 8.220.09 Carbon Dioxide 0.86 0.86 0.00 0.82 0.86 0.04 0.82 0.84 0.01 0.820.83 0.01 Helium 0.35 0.32 −0.04 0.34 0.35 0.01 0.34 0.33 −0.01 0.340.33 −0.01 Hydrogen 0.01 0.01 0.00 0.82 0.68 −0.14 1.20 1.05 −0.15 1.200.97 −0.23 Oxygen 2554 ppm 0.14 — 0.10 0.02 −0.08 0.09 0.01 −0.08 0.090.01 −0.08 Methane 68.70  65.89 −2.80 68.37 69.51 1.14 67.80 67.21 −0.5967.80 69.76 1.96 Ethane 7.85 8.22 0.37 8.08 7.91 −0.18 7.86 8.43 0.587.86 7.80 −0.06 Propane 7.16 7.86 0.70 6.91 6.77 −0.14 7.20 7.88 0.687.20 6.74 −0.46 Iso-Butane 1.37 1.56 0.19 1.21 1.17 −0.05 1.41 1.43 0.021.41 1.19 −0.22 N-Butane 3.36 3.80 0.43 3.09 2.56 −0.53 3.52 3.51 −0.013.52 2.83 −0.69 Iso-Pentane 0.76 0.80 0.04 0.69 0.54 −0.15 0.82 0.76−0.06 0.82 0.63 −0.19 N-Pentane 0.74 0.76 0.02 0.65 0.45 −0.20 0.75 0.72−0.04 0.75 0.58 −0.18 Hexane+ 0.33 0.39 0.05 0.13 0.05 −0.08 0.15 0.14−0.01 0.15 0.11 −0.04

TABLE 2 Detailed C₆ ⁺ Composition of Inlet and Outlet Streams ofDeoxygenation Reactor with Various Catalysts Run 1 Run 2 Run 3 Run 4Inlet Outlet Change Inlet Outlet Change Inlet Outlet Change Inlet OutletChange Component Mole % Mole % Mole % Mole % Mole % Mole % Mole % Mole %Mole % Mole % Mole % Mole % 2,2-dimethylbutane 0.0030 0.0101 0.00710.0003 0.0000 −0.0003 0.0001 0.0003 0.0002 0.0001 0.0001 0.00002,3-dimethylbutane 0.0056 0.0228 0.0172 0.0022 0.0003 −0.0019 0.00500.0082 0.0032 0.0050 0.0016 −0.0034 2-methylpentane 0.0369 0.0300−0.0069 0.0094 0.0030 −0.0064 0.0091 0.0203 0.0112 0.0091 0.0098 0.00073-methylpentane 0.0382 0.0223 −0.0159 0.0256 0.0087 −0.0169 0.02210.0359 0.0138 0.0221 0.0248 0.0027 Methylcyclopentane 0.0372 0.08030.0431 0.0209 0.0060 −0.0149 0.0365 0.0221 −0.0144 0.0365 0.0169 −0.0196Benzene 0.0027 0.0048 0.0020 0.0016 0.0006 −0.0010 0.0005 0.0002 −0.00030.0005 0.0002 −0.0003 Cyclohexane 0.0262 0.0194 −0.0068 0.0110 0.0051−0.0059 0.0023 0.0017 −0.0006 0.0023 0.0031 0.0008 n-hexane 0.12770.1114 −0.0163 0.0483 0.0144 −0.0339 0.0644 0.0461 −0.0183 0.0644 0.0440−0.0204 2,2-dimethylpentane 0.0023 0.0070 0.0047 0.0001 0.0002 0.00010.0011 0.0002 −0.0009 0.0011 0.0012 0.0001 2,4-dimethylpentane 0.00570.0118 0.0061 0.0005 0.0014 0.0009 0.0006 0.0001 −0.0005 0.0006 0.00060.0000 3-methylhexane 0.0057 0.0078 0.0020 0.0010 0.0029 0.0019 0.00070.0004 −0.0003 0.0007 0.0007 0.0000 1,t3-dimethylcyclopentane 0.00070.0009 0.0002 0.0000 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.00000.0000 1,c3-dimethylcyclopentane 0.0006 0.0005 −0.0001 0.0001 0.00040.0003 0.0000 0.0000 0.0000 0.0000 0.0000 0.00001,t2-dimethylcyclopentane 0.0002 0.0004 0.0001 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Toluene 0.0008 0.0016 0.00080.0001 0.0004 0.0003 0.0004 0.0002 −0.0002 0.0004 0.0000 −0.0004Methylcyclohexane 0.0049 0.0038 −0.0011 0.0012 0.0020 0.0008 0.00290.0035 0.0006 0.0029 0.0030 0.0001 Ethylcyclopentane 0.0000 0.00310.0031 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000n-heptane 0.0217 0.0345 0.0128 0.0019 0.0024 0.0005 0.0024 0.0022−0.0002 0.0024 0.0027 0.0003 2,4 + 2,5-dimethylhexane 0.0003 0.00300.0026 0.0000 0.0000 0.0000 0.0002 0.0003 0.0001 0.0002 0.0005 0.00031,t2,c4-trimethylcyclopentane 0.0001 0.0002 0.0001 0.0001 0.0000 −0.00010.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,t2,c3-trimethylcyclopentane0.0002 0.0002 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 2-methylheptane 0.0002 0.0015 0.0013 0.0000 0.0001 0.00010.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,c2,t4-trimethylcyclopentane0.0002 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 3-methylheptane 0.0006 0.0002 −0.0004 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,c3-dimethylcyclohexane0.0003 0.0001 −0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 1,t4-dimethylcyclohexane 0.0004 0.0000 −0.0004 0.00010.0000 −0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000methyl-ethylcyclopentanes 0.0002 0.0000 −0.0002 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,C4&1,t3-dimethylcyclohexane0.0006 0.0000 −0.0006 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 1,c2-dimethylcyclohexane 0.0007 0.0001 −0.0006 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Ethylcyclohexane0.0002 0.0001 −0.0001 0.0000 0.0001 0.0001 0.0000 0.0000 0.0000 0.00000.0000 0.0000 Ethylbenzene 0.0003 0.0004 0.0001 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 m + p-xylene 0.0005 0.0005−0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000o-xylene 0.0001 0.0016 0.0014 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 0.0000 n-octane 0.0060 0.0093 0.0033 0.0004 0.0002 −0.00020.0000 0.0000 0.0000 0.0000 0.0003 0.0003 Trimethylhexanes 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000Dimethylheptanes 0.0002 0.0000 −0.0002 0.0000 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 Isopropylcyclopentane 0.0001 0.0000−0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000n-propylcyclopentane 0.0001 0.0000 −0.0001 0.0000 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 3-methyloctane 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000Trimethylcyclohexanes 0.0001 0.0001 −0.0001 0.0000 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 Isopropylbenzene 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000Isopropylcyclohexane 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 n-propylcyclohexane 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000n-propylbenzene 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 m-ethyltoluene 0.0002 0.0000 −0.0002 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 p-ethyltoluene0.0001 0.0000 −0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 1,3,5-trimethylbenzene + 4,5- 0.0000 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 methylnonaneo-ethyltoluene + 3-methylnonane 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,2,3-trimethylbenzene0.0000 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 n-nonane 0.0002 0.0001 −0.0001 0.0001 0.0000 −0.00010.0000 0.0000 0.0000 0.0000 0.0000 0.0000 2-methylnonane 0.0001 0.00010.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000tert-butylbenzene 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 1,2,4-trimethylbenzene 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000Isobutylcyclohexane + 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 t-butylcyclohexane isobutylbenzene0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 sec-butylbenzene 0.0001 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 n-butylcyclohexane 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000 1,3-diethylbenzene 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 1,2-diethylbenzene + 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000 n-butylbenzene 1,4-diethylbenzene 0.0000 0.0001 0.0001 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 n-decane 0.00080.0004 −0.0004 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000 unidentified C9 naphthenes + C10 0.0002 0.0001 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 paraffinsunidentified C10 aromatics + C11 0.0001 0.0002 0.0001 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 paraffins UngroupedC10's 0.0001 0.0001 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 0.0000 n-undecane 0.0000 0.0000 0.0000 0.0000 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 isododecane+ 0.00000.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.00000.0000

The preferred forms of the invention described above are to be used asillustration only, and should not be used in a limiting sense tointerpret the scope of the present invention. Obvious modifications tothe exemplary embodiments, set forth above, could be readily made bythose skilled in the art without departing from the spirit of thepresent invention.

The inventors hereby states their intent to rely on the Doctrine ofEquivalents to determine and assess the reasonably fair scope of thepresent invention as pertains to any apparatus not materially departingfrom but outside the literal scope of the invention as set forth in thefollowing claims.

We claim:
 1. A process for removing oxygen from a natural gas stream,said process comprising: (a) combining an oxygen-containing natural gasstream with a reducing agent to form a combined gas stream; and (b)contacting at least a portion of said combined gas stream with at leastone copper-containing catalyst in a deoxygenation zone to therebyprovide an oxygen-depleted gas stream, wherein said contacting iscarried out under conditions sufficient to maintain at least a portionof the copper of said copper-containing catalyst in a reduced stateduring said contacting.
 2. The process of claim 1, wherein saidcontacting is carried out under conditions sufficient to maintain atleast 40 percent of the copper of said copper-containing catalyst in areduced state during said contacting of step (b).
 3. The process ofclaim 1, wherein said reducing agent comprises hydrogen.
 4. The processof claim 1, wherein said contacting of step (b) is carried out at anaverage temperature of at least about 350° F. and not more than about480° F.
 5. The process of claim 1, wherein the molar ratio of hydrogento oxygen in said combined gas stream is not 2:1.
 6. The process ofclaim 5, wherein the molar ratio of hydrogen to oxygen in said combinedgas stream is less than 2:1.
 7. The process of claim 1, wherein the pHof said oxygen-depleted gas stream is at least
 5. 8. The process ofclaim 1, wherein said combining of step (a) is carried out prior to saidcontacting of step (b).
 9. The process of claim 1, wherein saidoxygen-containing natural gas stream comprises oxygen in an amount of atleast about 50 parts per million by weight (ppmw) and not more thanabout 15,000, ppmw, based on the total weight of said oxygen-containingnatural gas stream.
 10. The process of claim 1, further comprising,during at least a portion of said contacting of step (b), adjusting theamount of hydrogen combined with said oxygen-containing natural gasstream.
 11. The process of claim 1, wherein said oxygen-containingnatural gas stream comprises C₁ to C₆ hydrocarbons in an amount of atleast about 25 weight percent, based on the total weight of saidoxygen-containing natural gas stream.
 12. The process of claim 1,wherein said oxygen-containing natural gas stream comprises less thanabout 15 weight percent of one or more inert gases selected from thegroup consisting of nitrogen, neon, xenon, argon, helium, krypton,radon, and combinations thereof.
 13. The process of claim 1, furthercomprising, prior to said combining of step (b), removing at least aportion of one or more sulfur-containing compounds from a natural gasstream to thereby provide a desulfurized natural gas stream, whereinsaid oxygen-containing natural gas stream combined with said reducingagent comprises said desulfurized natural gas stream.
 14. A process forremoving oxygen from a natural gas stream, said process comprising: (a)introducing oxygen-containing natural gas and hydrogen into adeoxygenation zone, wherein said hydrogen is present in saiddeoxygenation zone in a non-stoichiometric amount relative to the amountof oxygen present in said deoxygenation zone; and (b) removing at leasta portion of the oxygen from the natural gas with at least one catalystin said deoxygenation zone to thereby provide an oxygen-depleted naturalgas stream, wherein the average temperature of said deoxygenation zoneis less than about 480° F.
 15. The process of claim 14, wherein saidhydrogen is present in a sub-stoichiometric amount relative to theamount of oxygen present in said deoxygenation zone.
 16. The process ofclaim 14, wherein said catalyst is a copper-containing catalyst.
 17. Theprocess of claim 16, wherein the average temperature of saiddeoxygenation zone is at least 325° F.
 18. The process of claim 14,wherein said oxygen-depleted gas stream comprises less than about 25ppmw of oxygen, based on the total weight of said oxygen-depleted gasstream.
 19. The process of claim 14, further comprising, measuring thehydrogen content and/or oxygen content of said oxygen-depleted gasstream and, based on the measured value of said hydrogen and/or oxygencontent of said oxygen-depleted gas stream, adjusting the amount ofhydrogen introduced into said deoxygenation zone and/or adjusting theaverage temperature of said deoxygenation zone.
 20. The process of claim14, wherein said oxygen-depleted gas stream comprises less than 20percent of the total amount of oxygen introduced into the deoxygenationzone.
 21. A method for controlling a process for removing oxygen from agas stream, said method comprising: (a) combining an oxygen-containingfeed gas stream with a hydrogen stream to thereby provide a combinedfeed gas stream; and (b) passing at least a portion of said combinedfeed gas stream through a deoxygenation zone, wherein said passingcomprises contacting said combined feed gas stream with at least onecatalyst to remove at least a portion of the oxygen from said combinedfeed gas stream and provide an oxygen-depleted gas stream; (c) measuringa value for at least one parameter of said oxygen-depleted gas stream;(d) comparing the measured value for said parameter of saidoxygen-depleted gas stream determined in step (c) with a target valuefor said parameter of said oxygen-depleted gas stream to determine adifference; and (e) based on said difference, controlling at least oneparameter of said combined gas stream in order to minimize saiddifference.
 22. The method of claim 21, wherein said parameter of saidoxygen-depleted gas stream measured in step (c) is selected from thegroup consisting of the amount of oxygen in said oxygen-depleted gasstream, the amount of hydrogen in said oxygen-depleted gas stream, thepH of said oxygen-depleted gas stream, and combinations thereof.
 23. Themethod of claim 21, wherein said parameter of said combined gas streamcontrolled in step (e) is selected from the group consisting of themolar ratio of hydrogen to oxygen of said combined gas stream, thetemperature of said combined gas stream, and both the molar ratio ofhydrogen to oxygen and the temperature of said combined gas stream. 24.The method of claim 21, wherein said measuring of step (c) includesdetermining a value for the oxygen content of said oxygen-depleted gasstream, and wherein step (d) comprises comparing the measured value forsaid oxygen content of said oxygen-depleted gas stream determined instep (c) with a target value for said oxygen content of saidoxygen-depleted gas stream to determine said difference.
 25. The methodof claim 24, wherein said target value is a maximum oxygen limit,wherein said oxygen content of said oxygen-depleted gas stream measuredin step (c) is higher than said maximum oxygen limit, wherein saidcontrolling of step (e) includes increasing the molar ratio of hydrogento oxygen in said combined gas stream and/or increasing the temperatureof said combined gas stream.
 26. The method of claim 24, wherein saidtarget value is a minimum oxygen limit, wherein the oxygen content ofsaid oxygen-depleted gas stream measured in step (c) is lower than saidminimum oxygen limit, wherein said controlling of step (e) includesreducing the molar ratio of hydrogen to oxygen in said combined gasstream.
 27. The method of claim 21, wherein said measuring of step (c)includes determining a value for the hydrogen content of saidoxygen-depleted gas stream and wherein said comparing of step (d)comprises comparing the value for said hydrogen content of saidoxygen-depleted gas stream measured in step (c) with a target value forsaid hydrogen content of said oxygen-depleted gas stream to determinesaid difference.
 28. The method of claim 21, wherein said measuring ofstep (c) includes determining a value for the pH said oxygen-depletedgas stream and wherein said comparing of step (d) comprises comparingsaid value for said pH of said oxygen-depleted gas stream determined instep (c) with a target value for said pH of said oxygen-depleted gasstream to determine said difference.
 29. The method of claim 21, furthercomprising, repeating steps (a) through (e) until said difference has avalue that is not more than about 10 percent of said target value. 30.The method of claim 21, wherein at least a portion of steps (a) through(e) are carried out with an automated control system.